(a) Field of the Invention
The present invention relates to a liquid crystal display having a wide viewing angle.
(b) Description of the Related Art
Generally, a conventional liquid crystal display (LCD) includes two substrates having electrodes and liquid crystal injected therebetween. The voltage difference between the electrodes yields an electric field, and the molecules of the liquid crystal are re-arranged by the electric field. The polarization of incident light is varies due to the re-arrangement of the liquid crystal molecules.
Hereinafter, the conventional LCD is explained in detail with reference to the accompanying drawings.
FIGS. 1A and 1B are sectional views of a conventional twisted-nematic liquid crystal display (TN-LCD). The TN-LCD in FIG. 1A includes transparent glass substrates 1 and 2 facing each other, a liquid crystal layer 7 inserted between the substrates 1 and 2, and electrodes 3 and 4 formed respectively on the inner surfaces of the substrates 1 and 2, and polarizing plates 5 and 6 for polarizing the light are attached to the outer surfaces of the glass substrates 1 and 2 respectively.
The electrode 3 of the lower substrate 1 is a pixel electrode, the electrode 4 of the upper substrate 2 is a common electrode, and dielectric anisotropy xcex94xcex5 of the liquid crystal layer 7 is positive.
In the absence of an electric field, the long axes of the liquid crystal molecules 8 of the liquid crystal layer 7 are parallel to the substrates 1 and 2, and the liquid crystal molecules 8 are twisted spirally from one substrate to the other substrate.
When a power V is connected to the electrodes 3 and 4, and a sufficient electric field is applied to the liquid crystal layer 7 in the direction of the arrow as illustrated in FIG. 1B, the long axes of the liquid crystal molecules 8 are parallel to the direction of the electric field. This type of TN-LCD unfortunately results in having a narrow viewing angle.
An object of the present invention is to provide a liquid crystal display (LCD) having a wide viewing angle to substantially obviate the problems associated with the related art.
An LCD according to embodiments of the present invention includes a liquid crystal material between first and second substrates, and the liquid crystal molecules are perpendicular to the two substrates. First and second electrodes are formed on one of the two substrates and substantially parallel to each other.
Alignment films for aligning molecular axes of the liquid crystal molecules to be perpendicular to the substrates may be formed on the first and/or the second substrates, and the alignment films may be or may not be rubbed.
In addition, the LCD of the present invention may further include polarizing plates, and the polarizing directions of the polarizing plates are either parallel or perpendicular to each other.
Here, the dielectric anisotropy of the liquid crystal material may be positive or negative, and the liquid crystal may be at least one among pure nematic liquid crystal, chiral nematic liquid crystal and nematic liquid crystal having chiral dopants.
When voltage is applied to the two electrodes of the LCD of the present invention, a parabolic electric field is generated between the two electrodes, and the liquid crystal molecules are re-arranged in response to the electric field.
The liquid crystal display described above is called an electrically-induced optical compensation liquid crystal display (EOC-LCD) hereinafter.
In the EOC-LCD according to the embodiments of the present invention, the liquid crystal molecules are symmetrically aligned to the surface which is equal distance from each of the electrodes. Accordingly, the phase retardation of the transmitted light is symmetrically compensated, thereby obtaining a wide viewing angle.
The electrodes are preferably bent to form a saw shape in a pixel or by pixel in order to vary the orientations of the liquid crystal molecules.
When using the cross polarizing plates, it is preferable that the polarizing directions of the polarizing plates are neither parallel nor perpendicular to the directions of the electrodes. It is more preferable that the angle between the polarizing directions of the polarizing plates and the electrodes is 45 degrees.
The bent angle of the electrodes may be between zero and 180 degrees, but it is most preferable that the bent angle of the electrodes is 90 degrees.
Additional objects and advantages of the present invention are set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.